Engine starters



July 24, 1956 s. GILBERT ENGINE STARTERS Original Filed May 19, 1949INVENTOR. SAMUEL G/LBERT HTTORA/Er tate Patent 01 2,755,642 PatentedJuly 24, 1956 ENGINE STARTERS Samuel Gilbert, Qedar Grove, N. J.,assignor to Bendix Aviation Corporation, Teterboro, N. 1., a corporationof Delaware Continuation of application Serial No. 94,091, filed May 19,1949. This application April 28, 1954, Serial No. 426,062

3 Claims. (Cl. 64-30) The present application is a continuation of U. S.application Serial No. 94,091 filed May 19, 1949, and relates to enginestarters and more particularly to direct cranking engine starters.

In starters of the type having a rotatable barrel internally connectedthrough an interleaved friction disc pack to a spline nut, it isnecessary to have the spline nut centered accurately within the barrelin order to ob tain smooth operation of the clutch. In order to keep thespline nut centered it has been customary, as shown in Lansing U. S.Patent No. 2,064,670, granted December 15, 1936, to use a solid guidebushing aflixed to the spline nut and having a relatively smallclearance between the barrel and the bushing. This arrangement, however,has proven unsatisfactory for certain applications due to the wide rangein temperature to which the starter is subjected. Thus, if the bushingis fitted with a proper clearance at normal temperatures, the clearancebecomes entirely too large for operation at sub-zero temperatures andtoo small at high temperatures due to the thermal coefficient ofexpansion of the bushing. This change in clearance in either directionadversely affects the operation of the disc pack by causing unevenpressure thereon due to the misalignment of the spline nut.

One object of the present invention is to provide simple means wherebythe objections of the above described centering arrangement may beavoided.

Another object of the present invention is to provide a novelarrangement in a starter of the above mentioned type whereby the splinenut is kept in alignment with the driving barrel irrespective oftemperature changes.

Another object of the present invention is to provide means whereby aslight modification of a conventional spline nut guide bushing willsubstantially prevent changes of the outside diameter thereof withchanges in temperature.

Still another object of the present invention is to provide simple meansfor preventing a cylindrical member from changing its outside diameterwith changes in temperature.

The above and other objects and features of the invention will appearmore fully hereinafter from a consideration of the following descriptiontaken in connection with the accompanying drawing wherein one embodimentof the invention is illustrated by way of example.

In the drawings:

Figure 1 is a view partly in section and partly in ele vation of astarter embodying the present improvement.

Figure 2 is a view taken along line 2-2 of Figure 1.

The starter shown in Figure l is of a type well known in the art andcomprises a jaw actuating mechanism generally indicated at it? adaptedto extend starter jaw 12 into engagement with engine jaw 14 and drivenfrom a motor output pinion 16 through planetary gearing 18 and enclosedby housing 29. As is well known, rotation of barrel 22 of jaw actuatingmechanism is transmitted to axially stationary spline nut 24 through atorque limiting disc pack 26. The long lead internal threads of thespline nut mesh with corresponding threads of screw 28 which isconnected to starter jaw 12 by axial splines 30 for rotation therewith.

Starter jaw 12 and screw 28 are restricted against rotation by frictionexerted against the starter jaw 12 by a friction ring 36 and oil seal 38which is sufficient to prevent the screw from rotation with the splinenut. Rotation of spline nut 24 moves screw 28 to the left as viewed inthe drawing until shoulder 32 of the screw 23; abuts correspondingshoulder 34 of the spline nut 24 and hence forces starter jaw 12 intodriving engagement with the engine jaw 14. Upon the shoulder 32 abuttingthe shoulder 34, the friction exerted against the starter jaw 12 isovercome and it rotates with the screw 28 to crank the engine.

The planetary gearing 18 as shown comprises the motor output pinion 16functioning as the sun gear, a stationary orbit gear .6 shown as beingintegral with starter housing 2% and one or more planet gears 42 mountedon end wall 44 of the barrel 22.

Starter housing 20 is provided with a flange 46 for mounting on anengine mount indicated at 43 with bolts 4% as shown.

In starters of this type a spline nut guide bushing 50 is provided inorder to maintain the spline nut 24 in a centered position relative tothe barrel 22. This guide bushing Eli also serves as a pressure platefor the disc pack 26 as shown and is placed between outwardly extendingflange 52 of spline nut 24 and the disc pack 26. Recesses are formed inthe spline bushing on the face abutting the flange 52 of the spline nut24 in order to provide grease pockets to insure proper lubrication.

The discs of disc pack 26 are forced into the frictional engagement witheach other by a plurality of circumferentially spaced springs 60compressed between flange 52 and an adjustable nut 62 threaded into thebarrel and set so that the disc pack 26 will slip at a predeterminedtorque thereby permitting relative motion between the spline nut 24 andthe barrel 22 should the engine abnormally resist cranking or if theengine should backfire.

Heretofore clearance 64 between the guide bushing 50 and the barrel 22had to be made sufficiently large to prevent the guide bushing frombinding with the barrel 22 at the highest temperature to which the guidebushing 50 might be exposed during normal operation of the starter.During extremely cold weather, however, the guide bushing 58 willcontract and the outside diameter thereof decrease to such an extent asto make it ineffective to center the spline nut 2 properly within thebarrel 22. The resulting misalignment between the spline nut 24 andbarrel 2% will cause erratic clutch values.

In the solution of the problem here involved, it should be recognizedthat the annular length of the bushing is relatively much greater thanthe width of the sleeve of the bushing so that changes in effectivetemperature will cause relatively greater change in the annular lengthof the bushing than the relatively minor change in the width of thesleeve of the bushing. In a bushing of the solid type such change in theannular length of the bushing will in'tu-rn cause greater change in theouter diameter of the bushing than does the relatively negligible changein the width of the sleeve of the bushing due to such change in thetemperature aifecting the bushing.

The bushing 50, as shown in Figure 1, is located adjacent the clutchpack 26 of the starter and is in what is commonly referred to as a hotspot and is subject to the high temperatures resulting upon slippage orfriction at the clutch pack 25. Such high temperatures at the hot spotto which the bushing 50 is subject causes a relatively great increase inthe annular length of the bushing 50 and in the case of a solid bushinga corresponding increase in the outer diameter of the bushing tending tocause the bushing to seize or bind with the barrel 22, unless theclearance 64 be made excessively large with the attendant difliculties,as heretofore explained. In order to avoid these difliculties, there isprovided the arrangement of the split bushing 50, as herein explained.

According to the present invention the objectionable changes in theoutside diameter of the spline guide bushing 50 with variations oftemperature are made negligible by cutting a relatively narrow slit 66through the bushing 50 as indicated in Figure 2. The width of the slit66 is determined by the temperature coefficient of expansion of thebushing 50. By selecting the width of the slit 66 so that it is almostclosed at the highest temperature to which the bushing 50 may be exposedand having the split bushing 50 so formed that under cold operatingconditions, the bushing 50, when unconfined, has an innercircumferential surface normally of smaller diameter than the peripheryof flange 52 so that under cold or extremely low temperatures thebushing 50 when positioned on the flange 52, as shown in Figure 1, makesa tight fit on the flange 52 of spline nut 24 and under hightemperatures bushing 50 may expand causing the diameter of the innercircumferential surface thereof to tend to approach substantially thesame diameter as that of the periphery of flange 52 and under which hightemperature conditions slit 66 is almost closed, so that, as shown inFigure l, the clearance 64 may be accurately preset to a predetermineddesirable value which clearance will not be substantially affected byvariation in temperature.

The split bushing 50, as shown in Figure 1, bears upon and is internallyconfined by the flange 52 of the spline nut 24 so that upon an increasein temperature the annular length of the split bushing 50 expands, butinstead of forcing the peripheral edge of the bushing 50 outward, as inthe case of a solid bushing, the ends of the split bushing 50 expandannularly about the flange 52 while upon a decrease in the temperatureaifecting the split bushing 50, the free ends thereof contract annularlyincreasing the width of the slit 66.

Thus such expansion and contraction of the split bushing in a lengthwiseor annular sense (as distinguished from the relatively minor change inthe width of the sleeve portion of the bushing 50) will not cause asubstantial change in the overall diameter of the split bushing 50, asin the case of a solid bushing, since the slit 66 in the split bushing50 permits such change in the annular length of the bushing 50 without asubstantial change in the outer diameter or peripheral edge of the splitbushing 50.

The ends of the split bushing 50 being unconfined in the slit 66 maytherefore expand freely around the flange 52 without causing acorresponding expansion in the outer diameter of the bushing 50 as wouldbe characteristic with a bushing of the solid type due to thecircumferential expansion thereof.

The arrangement of the split bushing 50 thus permits a greater expansionof the annular length of the bushing 59 without substantial change inthe outer diameter of the bushing 50 and thus permits closer fits thanwould a bushing of the solid type, such as shown in the Lansing U. S.Patent No. 2,064,670, made of a like material.

It is thus seen that the bushing will provide proper centering for thespline nut 24 relative to the barrel 22 at all times because the widthof the slit 66 will increase or decrease with changes in temperature andthe over-all diameter of the bushing 50 will remain substantially consstant, or in other words the slit 66 acts as means for pro vidingannular expansion and contraction of the bushing to prevent radialexpansion and contraction thereof.

Although only one embodiment of the invention has been illustrated anddescribed, various changes in the form and relative arrangements of theparts may be made to suit requirements.

What is claimed is:

1. In a starter having a driving barrel member, an annular member withinsaid barrel member, and means for driving said annular member from saidbarrel member; the improvement comprising means for centering saidannular member within said barrel member including an annular splitbushing surrounding said annular member and bearing upon a portion ofsaid annular member, said bushing being of a size so as to provideclearance between said bushing and said barrel, said split bushing beingnormally subject to annular expansion and contraction with changes oftemperature and under extreme low temperatures having an innercircumferential surface normally of smaller diameter than the peripheryof said annular member so as to make a tight fit on the annular memberunder the last mentioned low temperatures, said split bushing expandingwith increase in temperature so as to cause the inner circumferentialsurface thereof to approach under maximum permissible temperaturessubstantially the same diameter as that of the periphery of said annularmember, said split bushing having free ends defining a radial slit insaid bushing, said slit permitting free movement of said ends relativeone to the other upon the annular expansion and contraction of saidbushing upon changes in temperature, and thereby substantially lessenradial expansion and contraction of said bushing due to said changes intemperature, and said radial slit being so proportioned as to besubstantially closed when subjected to the high end of the temperaturerange.

2. In a starter having a driving barrel member, an annular driven memberwithin said barrel member and means for drivingly connecting said barrelmember with said driven member; the improvement comprising annularcentering means for said driven member mounted thereon and rotatabletherewith, said centering means having a running clearance between thecircumference thereof and said barrel member, said centering means beinga ring-like member mounted on said driven member and normally subjectedto annular expansion and contraction due to temperature changes, saidring-like member having a slit therethrough, said ring-like member underextreme low temperatures having an inner circumferential surfacenormally of smaller diameter than the periphery of said annular drivenmember so as to make a tight fit on the annular driven member under thelast-mentioned low temperatures, said ring-like member expanding withincrease in temperature so as to cause the inner circumferential surfacethereof to approach under maximum permissible temperatures substantiallythe same diameter as that of the periphery of said annular drivenmember, the slit through said ring-like member permitting the annularcontracting and expansion of the ring-like member upon changes intemperature so as to substantially prevent upon said annular expansion acorresponding radial expansion of said ring-like member and seizure ofthe ring-like member with the barrel member, the width of said slitbeing determined by the coetficient of expansion of said ring-likemember to provide a minimum opening for all temperatures.

3. In a starter having a rotatable barrel, a rotatable spline nutadapted to extend a jaw member into engagement with an engine jaw memberof an engine to be started, a torque limiting disc pack providingdriving connection between said barrel and said spline nut, and anoutwardly extending annular flange member on said spline nut; theimprovement comprising an annular ring member rotatable with said splinenut and forming the pressure plate for said disc pack, said ring memberinterposed between said flange member and said disc pack and being ofsuch a size as to have a close running clearance with said barrel, saidring member having a radial slit therethrough and free ends movablerelative one 5 to the other, said ring member under extreme lowtemperatures having an inner circumferential surface normally of smallerdiameter than the periphery of said annular flange member so as to makea tight fit on the annular flange member under the last mentioned lowtemperatures, said ring member expanding with increase in temperature soas to cause the inner circumferential surface to approach under maximumpermissable temperature substantially the same diameter as that of theperiphery of said annular flange member, the free ends of said ringmember being movable upon annular expansion of said ring member withincrease in temperature due to friction at said disc pack so as tolessen radial expansion of the ring member to prevent seizure of thering member in the barrel, said slit being proportional to thetemperature coeflicient of expansion of said ring member.

References Cited in the file of this patent UNITED STATES PATENTS2,064,670 Lansing Dec. 15, 1936

